In the electronics industry, there is a constant demand for electronic devices, such as integrated circuits (ICs) or semiconductor chips, to be produced less expensively and in smaller dimensions. One way to increase productivity of such electronic devices, and thereby reduce their unit cost, is to increase the test speed of the devices by testing a plurality of them at the same time.
Such an electronic device test system (IC tester, for example) comprises a master unit for generating various test signals and for evaluating the resulting output signals and an automatic test handler for automatically transferring the devices to be tested to test heads and sorting the tested devices based on the test results. Unfortunately, in a complicated test system for testing a large number of devices at the same time, the test system is not free form errors even when the system utilizes the state of the art technology. For example, this type of mechanical system is subjected to an error referred to as "jamming," wherein two or more electronic devices, or carrier modules and the like, stick together or stick to passages of the test system and cannot separate from one another. If such jamming occurs, it is usually necessary to stop the operation of the test system to clear the jam, thus causing a serious loss of time and decrease of efficiency. The other type of error is a mechanical error which is not directly caused by the devices to be tested but rather the test system itself, such as, for example, mechanical inaccuracy, errors in sensors, temperature control errors, or sorting errors.
Therefore, it is important, in such device testing, or in the automatic test handler to indicate an error in the test system and to accurately identify a position where an error exists as fast as possible so that such errors can be corrected. The faster the identification of the position of errors and the restoration of the normal operating condition, the more efficient the device testing becomes, thus increasing the productivity of the devices. The present invention deals with such an alarm display system for use in an automatic test handler in an electronic device test system to increase the test efficiency and thus to increase the productivity by decreasing the overall time required for the device testing.
In an automatic test handler, it has become a test technology standard to place a number of electronic devices to be tested on a test tray and position them to be engaged by a test head plate having a number of corresponding test contactors. An example of the test system for testing a plurality of electronic devices in a test tray is shown in the U.S. Pat. No. 4,926,118 to O'Connor et al.
In the O'Connor patent, one electronic device is placed on a seat of carrier module, and each carrier module is provided with one or more device seats. A number of modules are then positioned by column and row on the test tray. The test tray, having a number of such carrier modules, is arranged so as to be in vertical alignment (either above or below) with a test fixture.
The test fixture includes test contactors (test pins) for contact with the pins of each electronic device to be tested for supplying and receiving the test signals from the device. Each module is aligned with a corresponding test contactor so that when either the test tray or the test fixture are moved in a vertical direction toward the other, the contactor engages the electronic device positioned within the carrier module.
The contactor is provided with a number of test pins or leads which come into electrical communication with the leads of the electronic devices to be tested. The automatic test handler is electrically connected to a master unit of electronic device test system which includes a test signal generator for supplying a test signal to the device, and with a signal comparator for analyzing the results of the test. Based on such results, the electronic devices are transferred to another location in the test process and sorted for proper handling.
The O'Connor patent does not show how to monitor each operation stage of the test system and identify error positions, such as locations of jamming of the devices to be tested or jamming of the tested devices, or the temperature of the devices during the course of the test processes. Therefore, it requires a considerable amount of time to discover an error position and recover the test system from such errors since there is not an effective means for monitoring and indicating by alarm sounds and an alarm display of such error positions.
In a further conventional test handler, there was an example of alarm display devices to indicate an error position in the test system. An example of such a test handler is shown in FIG. 1. In the test handler 10 of FIG. 1, electronic devices to be tested are removed from their container, usually called a "magazine," and separated from one another by the force of gravity. That is, the electronic device to be tested is positioned in the magazines 14 initially at a vertically higher position of the housing 13 than the test head 19 and, by its own weight, is separated from the other devices such that it slidably descends to the test head 19. After the test, the electronic device descends further, due to gravity, to a lower position of the housing 12 than the test head so as to be sorted in the unloader section 16 into the unloader magazines 18a-18g depending on the test results.
Such conventional device test system, which utilizes the force of gravity to separate and transfer the electronic devices, has a relatively simple structure since the driving force for the device movement is based on the gravity and the number of devices to be simultaneously tested is limited, i.e., two or four. Therefore, the conventional test system 10 shown in FIG. 1 usually employs a display device 11 for showing locations wherein a device jamming had occurred.
An example of such display devices 11 is illustrated in FIG. 2. The display device of FIG. 2 typically employs a printed display plate made of, for example, plastic and light emitting diodes (LEDs) or plasma display panels for showing an error position in the test system. For example, the display panel is illustrated in FIG. 2 as a flow diagram that includes each of the function blocks in the test system. Such function blocks are, for example, loader, distributer, transfer, contactor, sorter and unloader. Each functional block is accompanied by a alarm point comprising an LED, for example, which emits light or blinks when an error occurs in the corresponding function block as shown by pilot lamps PL1-PL6 in FIG. 2. Therefore, the user of the test system is notified by the alarm display and also by the alarm sound that an error exists, and the general position or the function block where the error occurred is indicated.
However, the error display device of this kind has three inherent disadvantages. First, since such display is formed of a single layer of fixed display which only shows each function block of the system, one can tell from such display only a general position or a functional block of the tester which involves an error. Thus, although the alarm display can show that there is an error in the test system and indicate the appropriate position of such error, it is not possible to show a specific or more detailed position or kinds of the error in each of the function blocks. As a result, the alarm display of this kind is not adequate for a more complicated test system.
Second, since such an alarm display system in the conventional test system is a specifically made system for a specific test system with only a single layer of display, it is not possible to show a detailed position with respect to each device or test tray to be tested in a more complicated test system wherein a large number of electric devices are loaded, temperature controlled, transferred and tested, and unloaded in parallel at the same time. Although it may be possible for the conventional alarm display system to be arranged to show more detailed error positions in the test system by increasing the size of the display, it would be necessary to have a display which is impractically large. Therefore, it is impractical in the conventional test handler to install an alarm display system which is capable of showing the detailed information of an error.
Third, since such an alarm display system in the conventional test system is a specifically made system for a specific test system, when a different type of test system is employed, the alarm display system has also to be replaced with the one specifically designed for the type of test system. Therefore, the alarm display system in the conventional test handler is inflexible and cannot be employed in a different type of test handler.
Thus, in summary, an alarm display system for an automatic test handler is necessary which can immediately notify and indicate any errors in the test system for testing a large number of electronic devices at the same time in parallel. At the same time, there is an increasing demand for greater test productivity so as to reduce the cost of IC devices. Moreover, with the increase of the test productivity, the test system becomes more complicated, and thus, it is necessary to indicate a specific position where an error happens to correct the error within a short period of time.
Thus, there is a serious need in the electronic device industry such as in the integrated circuit manufacturers and the like for an alarm display system for automatic test handler which can overcome the problems and disadvantages described above.